The invention relates to a roller carriage.
Such a roller carriage is known from EP B1 675 829, which discloses a roller carriage having a carriage bottom below which a plurality of wheels is mounted, at least one of these being swingably mounted about a vertical swivel axis. The upper side of the roller carriage is provided with means capable of retaining the wheels of an overlying roller carriage when several roller carriages are stacked. For the fixed wheels, these retention means are formed by rectangular recesses in which the fixed wheels can stand stably, while for each of the swingably mounted wheels they are formed by a completely or partly annular guide track with outer and inner engagement areas which retain the swingably mounted wheels against rotation.
Roller carriages of this type are usually used for the transport of goods in the distribution network from a wholesaler to retailers. The roller carriages are then transported back to the wholesaler in the empty state, it being a widespread wish that the roller carriages can be stacked so as to take up as little space as possible during transport.
The roller carriage described in the above-mentioned European patent solves a general problem of roller carriages having swingably mounted wheels, viz. that normally the wheels have to be aligned in specific directions in order to be retained in recesses provided in the upper side of the underlying roller carriage. The stated solution allows the orientation of the swingably mounted wheels to be quite arbitrary, while still providing satisfactory retention of the wheels.
However, in particular for the roller carriages in which the stated guide track is formed by a bracket plate, it has been found that a stack of many roller carriages, e.g. as many as 20, may be unstable in spite of the good retention against rotation of the swingably mounted wheels, it being possible for the swingably mounted wheels to rotate slightly about the point where they stand on the bracket plate. The effect of this is the greater, the more roller carriages are stacked on top of each other, and the greater the risk is for the persons working with the roller carriages.
The object of the present invention is to provide a solution in which this instability is avoided.
This is achieved by constructing a roller carriage having a bottom frame, with a plurality of wheels on its lower surface, at least one of the wheels being swingably mounted so as to swing about a substantially vertical swivel axis that does not intersect an axis of rotation of the wheel. The bottom frame also has retention means on its upper surface to retain at least one swingable wheel of an overlying roller carriage. The retention means include a support face for supporting the wheel of the overlying roller carriage at a support point that is positioned on a circular arc concentric with the swivel axis of the wheel. The retention means also includes an outer engagement area extending at least partly around the swivel axis of the wheel, and an inner engagement area disposed between the swivel axis of the wheel and the outer engagement area. The outer and inner engagement areas cooperate to restrict rolling movement of the swingable wheel of the overlying roller carriage in a direction transverse to the axis of rotation of the of the wheel. In addition, at least one of the inner and outer engagement areas is provided with at least one projection adapted to engage the wheel, the projection being adapted to absorb forces in parallel with the axis of rotation of the wheel at a radial distance from the support point such that swinging of the wheel about the support point on the support face is essentially prevented for substantially any angular orientation of the wheel with respect to the projection.
This provides a roller carriage which supports each of the swingably mounted wheels on an overlying roller carriage at at least two points, viz. at the point on the rolling face of the wheel which stands on the support face of the bracket plate, and at a point along the inner and/or outer engagement areas. Hereby, increased retention of the swingably mounted wheels against rotation about the swivel axis is obtained.
As a result of this increased retention, a quite stable stack of roller carriages can be obtained.
When the outer and inner engagement areas are arranged along concentric circles a particularly effective retention is obtained, as these can hereby normally support the swingably mounted wheels quite optimally against rotation in their rolling direction entirely independently of the angular orientation of the wheel.
The projection or projections which are to retain a swingably mounted wheel, may either be provided in connection with the inner engagement area or in connection with the outer engagement area.
The projection preferably consists of a pin or the like in connection with the inner engagement area, capable of engaging a groove which is provided in the rolling face of the swingably mounted wheel.
Alternatively, or as a supplement, several projections may be arranged in connection with the outer engagement area, and these are preferably arranged so that their mutual distance either corresponds to the width of the wheel, or so that they can engage an annular groove provided in the rolling face of the wheel.